The present invention relates to an improved method for the decomposition of hazardous halogen-containing organic compounds, such as polychlorinated biphenyls.
The potential hazard to public health and the environment posed by the indiscriminate disposal of a variety of synthetic halogen-containing organic chemicals is well known. Compounds such as polychlorinated biphenyls (PCBs), dichlorodiphenyltrichloroethane (DDT), decachlorooctahydro-1,3,4-metheno-2H-cyclobuta-[c,d]-pentalen-2-one(Kepone .RTM.), and 2,4,5-trichlorophenoxyacetic acid, (2,4,5-T) although having demonstrated utility, have been found in recent years to be persistent environmental poisons and, therefore, require a safe and effective means of disposal.
Halogenated organic compounds present a difficult disposal problem because of the highly stable nature of the carbon-halogen bonds present therein. The bond energy of a carbon-chlorine bond, for example, is on the order of 84 kcal./mole. Thus, many halogenated organic compounds are not only resistant to biodegradation, they cannot be degraded in a practical and effective manner by any of the well-known chemical decomposition methods. In most cases, known methods such as chlorolysis, catalytic dehydrohalogenation, molten salt reactions, ozone reactions and alkali metal reduction achieve only partial dehalogenation. Moreover, these prior art methods typically involve one or more drawbacks, such as the use of expensive reagents, inert atmospheres, extensive temperature control, complex apparatus, substantial energy consumption and the like.
In our U.S. patent applications Ser. Nos. 142,865 and 158,359, filed Apr. 21, 1980 and June 11, 1980, respectively, there is disclosed and claimed a method for the decomposition of halogenated organic compounds, especially PCBs, which represents a significant advance over the aforementioned methods of the prior art. The decomposition reagent used in practicing that method is produced by reacting an alkali metal, a polyglycol or a polyglycol monoalkyl ether, and oxygen. This reagent produces virtually complete dehalogenation of a variety of halogenated organic compounds, simply by mixing it with the halogenated compound in the presence of oxygen. Additional details of the methods of preparation and use of our previously discovered decomposition reagent are set forth in the two applications identified above, the full disclosures of which are incorporated herein by reference.
Continued efforts to improve our above-described method by enhancing its efficiency and reducing the cost and potential hazards involved in its operation, while maintaining the same high degree of effectiveness, have led to the development of the present invention.